marks



(No Mpdei.)

L. B. MARKS.

ELECTRIC ARC LIGHT.

Nd. 552,190. Patented Dec; 31, 1895.

1)OM. 5440 M01 7 loads ,5. Marks f 1% I 1 $3 GHQ-M42120 AKflKuA Nrrn STATES ATENT FFICEO Y., ASSIGNOR TO THE ELECTRIC ARC OF SAME PLACE;

ELECTRIC-ARC LIGHT.

SPECIFICATION forming part of Letters B Application filed October 9,

To aZZ whom it may concern:

Be it known that I, LOUIS B. MARKS, a citizen of the United States, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Electric-Arc Lighting, of which the following is a specification.

This invention relates to electric-arc lamps in which the arc burns within an inclosing transparent or translucent envelope to which the air has limited access. In lamps of this character heretofore patented by me (especially as described in Letters Patent No. 521,936, dated June 26, 1894) a special construction was arranged to prevent as far as practicable access of oxygen to the inclosing cylinder or envelope. It has been found that by reason of the exclusion of oxygen in this type of lamp the ohmic resistance of the arc stream is increased and hence the are requires a comparatively high-potential drop to insure steadiness. Vith a lowpotential drop the light is unsteady and the efficiency of the light is decreased and the negative electrode tends to build, thus impairing the practical operation of the lamp. There is also a marked tendency to deposit free carbon in the cylinder.

My. present invention is designed to maintain a low-potential drop across the arc in the various stages of service of a pair of electrodes,and at the same time maintaining a perfectly steady and efficient light to prevent the building of the negative electrode and the formation of nibs on the tip of the negative to improve the character of the contiguous points of the electrodes and preserve a desirable distribution of light and a uniform angle of illumination.

atent No. 552,190, dated December 31, 1895.

.. gerial No. 525,372. (No model.)

I have discovered that by regulating the temperature of a stream of heated air and so directing the application of the latter to the interior of the inclosing envelope that when entering the envelope the convection currents formed by the gases within will carry the air in a uniform direction with relation to the arc and the cylinder greatly improved results may be obtained as far as the-operation of this type of lamp on existing commercial circuits is concerned. No valve is used; but the envelope is provided with means for continually maintaining a steady circulation of gases, egress of gas and ingress of air or oxygen being carried on continuously and simultaneously. The limited quantity of air which is admitted may be directed over a path parallel to the are and electrodes or otherwise distributed so that the zone included between horizontal planes through the tips of positive and negative electrodes,respectively, receives the amount of oxygen desired. My present invention thus involves a method of feeding an are within an inclosure with a limited supply of oxygen and providing means whereby this supply may be maintained uniform and continuous. In the ordinary are light oxygen has unobstructed access to the are and carbon points. In the various types of inclosed arcs means are provided to exclude as far as possible the ingress of air or oxygen.

oxidizing agent in the inclosed arc lies in the great prolongation in longevity of electrodes. Incident to the exclusion of oxygen, however, are the increased resistance of the arc-stream, the shortening of the are for a given drop of potential, the flattening of the carbon points, the unsteadiness and inefficiency of the light at small potential differences, and the building of the negative at these potential differences. The increased resistance of the arcstream under the conditions just mentioned ters Patent were granted to me and another, No. 520,996, dated June 5,1894. It was found that under some conditions over twice the normal drop of potential'was necessary to efficiently run the form of inclosed are alluded to.

was the basis of an application for which Let- The chief advantage of the exclusion of an The shortening of the are for a given drop of potential due to surrounding the are by an inclosing medium and excluding oxygen has made it necessary in commercial operation of inclosed arcs to em ploy a higher drop per inclosed are than would be necessary for openair arcs, fora certain length of arcis required in order to produce a steady-light,and in the case of the inclosed are a greater potential difference is necessary to secure this length of arc than in the case of the open-air are. This follows naturally from the increased resistance of the inclosed are, as explained before. If the attempt be made to operate the inclosed are at as low-potential drops as-openair arcs, unsteadiness of the light results. Because of theflattening of the carbon .points due to being consumed in theabsence of an oxidizing agent the light is largely obscured an d the illumination effective onlyin'arsmall zone. Moreover, if operatedat as low (a potential-drop as an open-air are, the negative electrode invariably builds and a m ushroomshaped formation results. This formation consists largely of :graphitic carbon. The nib thus formed breaks cit eventually at its neck and flickering and unsteadiness of the light results.

Mypresent invention is designed toovercome or modify the actions just alluded to, and to provide for the production of an inclosed are which is applicable to commercial arc-light circuits'as they now exist.

A highly-important result which follows from the distribution of air-currentsias-described herein is that the resistance of the arc-stream, instead of being considerably increased, as is the case with other inclosed arcs, remains practically the same as in an openair are. The length of are for a given drop of potential is therefore not :less than but practically thesame as that-of an open-air arc of the same drop of potential.

Because of the flow of convection currents of are-gases admixed with atmospheric air the electrodes do not burnbluntas in ordinary inclosed arcs, but have much thesame shape as points formed in open air. The crater formed in the positive is substantially uniform in curvature, while the apex of thenegative is quite pointed and well centeredwith reference to the crater of the positive. Thus there is practically no obscurationof light as in theusual inclosed arcs where the-electrodes burn to blunt points. The light is steady andefficient at practically as low drop of potential as with open-air arcs. There is no building of the negative electrodes. There is no deposit or nib on the negative, the carbon-vapor from the positive being converted into gas and following the path of the eonvection currents. By virtue of thedirection of currents in the envelope the carbon deposit that would otherwise accumulate on-the tip of the negative and form a nib is attacked by a stream of oxygen-bearing gas and converted to carbon oxide, which is carried out of theenvelope in line with the upward convection currents. The position of the negative tip is maintained practically stationary in the envelope.

Various provisions may be made for directing the entering air over a path proper to attain the results above referredto. One form of construction which I have found to be successful in practice is to provide separate ducts for the outgoing and ingoing gases and so ob struct the progress of the gases through the ducts that air will be slowly but continuously and uniformly admitted and directed by deflectors into the .path normally takenby the convection currents existing in the envelope.

The several features of novelty of the invention will be more particularly hereinafter described, and will be definitelyindicated in the claims appended to this specification.

In'the accompanying drawings which illustrate one way of carrying out my invention, Figure 1 is a top .plan view, and Fig. 2aside elevation, partly in section, of a pair ofcarbons surrounded by an envelope provided with ingress and egress ducts in accordance with my invention.

An envelopeA .provideda't the top with a loosely fitting cap B touches the cylinder only at four projections a a a (L in the center of which is a circular or conical tube 0, through which the positiveelectrode D is fed to the arc. Thenegative electrode,by reason of its slower rate of consumption, may be smaller in diameter than the positive. The outer portion of the cap is enlarged into a bell-shaped flange, the rim of which is brought closely adjacent to the exterior wallof the envelope. Thus there is provided a narrow annular passage for the outside air into the envelope, one of the walls of this passage being formed by the envelope, which, by reason of its high temperature, heats the entering air in transit into the envelope. The tubular opening through which the electrode foods may with advantage be made slightly conical in shape, the enlargement at the top being onlya little'greater than the diameter of the electrode, so as to permit a free feed of the latter and to afford an obstructed egress for gases fromthe envelope.

The lower part of the tube may with advantage be fianged away from the electrode, as shown, this form serving as a defl ector for the upward currents around thepositive carbon, the flange at the same time forming a defleeting-wall for the in goingair and directing the latter outwardly toward the walls of the envelope. The tendency with this arrangement is \for all egress to take place by way of the central tubular opening and all ingress by way of the bell-shaped chamber.

An investigation of the convection currents within the envelope when a lamp is in operain the outer parts of the envelope and an upgoing current around the electrodes, as shown by the arrows in the drawings.

The arrangement of the cap hereinbefore described deflects the ingoing air into the downwardly-movin g portion of the convection current, where it is intimately mixed with the gases already formed in the envelope and raised in temperature, so that it is intensely hot by the time it reaches the arc. In the form of envelope shown in the drawings I have represented the bottom as closed and the outlet and inlet for the gases at the top. This, however, is not absolutely essential, although it is a convenient form to adopt in practice.

The essential feature of my invention is continuously and uniformly introducing limited quantities of air to the envelope and controlling the direction of their access to the arc and adjacent heated portions of the electrodes, so as to maintain a uniform condition of the arc in all stages of action of thelamp, a low drop across the arc and a uniform shape of the confronting electrodes. It is essential that electrodes of uniform texture be employed.

The rate of consumption of carbon in the inclosed arc, as described in my patents above referred to, is exceedingly small as compared with open-air arcs. Seven-sixteenths inch diameter by twelve inches total length are the dimensions of commercial plain carbons used in open-air arcs, and the average life is about seven hours. In the inclosed arc the average life of a pencil of the same length is more than ten times this amount, or over seventy hours. In the inclosed are, as claimed in the present invention, about fifty hours has been attained in practice. The continual inflow of oxygen in the direction of the convection currents in the latter case accounts for the reduction in life. However, the reduction of life is accompanied by several advantages of the greatest commercial value, which latter more than compensate for the decrease in longevity of electrodes. One of these advantages, the reduction in resistance of the are stream, due to presence of oxygen, is exceedingly valuable from a commercial standpoint, for with reduced resistance in the arc I am enabled to operate lamps at the voltages now commonly employed on open-air circuits.

It has been found that sixty to sixty-five volts are required for efficient operation of ordinary inclosed arcs. My present invention enables me 'to run at forty-five to fifty volts. Thus, assuming that I have a commercial ten-ampere constant'current circuit, each inclosed arc of the old type when applied to this circuit would require ten by sixty to ten by sixty-five or from sixhundred to sixty hundred and. fifty watts of energy. In the new type of inclosed arc the consumption of energy is reduced to from ten by fortyfive to ten by fifty or four hundred and fifty to five hundred watts, a saving of over twenty per cent. A type of the ordinary constanttry is designed to furnish an output of three thousand volts at nine and one-half to ten amperes. The capacity of such a machine, it will be seen, depends upon the number of volts consumed by each lamp on'the circuit. The reduction from sixty to sixty-five to forty-five to fifty volts thus enables me to increase the number of lamps that may be efficiently operated on each machine by over twenty per cent. Athree-thousand-volt machine will efficiently operate forty-eight inclosed arcs at sixty-two and one-half volts average each, whereas the same machine will operate sixty-three inclosed arcs at fortysevcn and one-half volts average each, no allowance being made in either case for line losses.

I have found that with solid carbons the shape of the crater in the positive electrode depends largely on the character of the formation at the tip of the negative electrode. If the negative tip is blunt there will be no perceptible crater in the positive, the latter be ing also blunt. If the negative burn to a sharp point and be well centered the crater in the positive will be comparatively deep and well centered. The importance of the proper formation and contour of the points with reference to distribution of light has been explained before. I am enabled, by utilizing the convection currents in the cylinder, as previously explained, to maintain the negative pointed during the operation of the lamp, and also to preserve a uniform crater in the positive. Both of these conditions are very favorable for a steady arc.

It is well known that a long are or one that requires an abnormally-large drop of potential produces a light rich in violet hue. This violet hue is objectionable for ordinary purposes of illumination. In my present invention, means having been provided for operating at normal potential drops, I have found that the presence of violet rays is largely reduced, the light being almost pure white. The best results have invariably been attained with small envelopes, such as referred to in my prior patents, when the envelope was three inches in diameter and four or five inches long, though I do not limit myself to any size. With a small cylinder the losses by radiation are very small, and gases can be kept at uniform temperature, 850.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-- 1. An arc lamp having a transparent or translucent inclosure around the are, provided with a small inlet for air and ducts for leading the air in a uniform direction rela tively to thearc.

2. An arc lamp having a transparent or translucent inclosure around the arc, a small ingress passage for air, an independent egress passage for the gaseous products of the are,

and deflecting walls for directing the entering air upon the are.

An arc lamp having" a transparent or translucent inclosure around the are provided with a narrow annular inlet for air, one of the inlet walls being formed by the cylinder whereby the air is heated before entering the are chamber.

4. An arc lamp provided with a transparent or translucent inclosure around the are, an opening in said inclosure for transit of the movable electrode, a tubular wall for said opening, a small inletzduct for airand means for directing the air toward the outer part of the inclosure.

In testimony whereof I have hereunto subscribed my name this 6th day of October, A. I). 1894:.

LOUIS B. MARKS.

Witnesses:

IDA KING SMITH, CARRIE L. MAXWELL. 

